Causes and impacts of Greenland atmospheric Blocking changes

该项目旨在促进对格陵兰上空大气环流变化的原因(特别是阻塞或持续高气压的变化)的理解，它们与北大西洋大气和海洋环流系统的变化的关系，它们对格陵兰和北大西洋/西北欧/英国地区气候变化和极端天气条件的影响，以及它们对格陵兰冰盖质量损失和全球海平面上升的影响。北半球中高纬度的高压阻塞是大气总体环流的一个重要特征，与人口稠密的中纬度地区的急流和极端天气事件密切相关。阻塞的物理原因以及它如何应对和影响更大范围的气候变化，尤其是在联系天气(每日)和气候(年际或更长时间)的时间尺度方面，人们了解得很少。最近的研究表明，自1990年左右以来，格陵兰地区的阻塞显著增加，主要是在夏季。目前可用的全球气候模型不能很好地模拟这一点。这一不足可能与最近北冰洋海冰的迅速减少有关，气候模型也没有很好地捕捉到这一点。然而，最新一代气候模型与以前的版本相比有了一些改进，尽管格陵兰块体的模型表示和观测表示仍然存在一些差异。我们的建议通过使用新方法、更新的观测数据和最新的气候模式模拟来综合比较来解决这种模型与观测的不匹配问题。我们试图通过从每天到十年的各种时间尺度上的观测数据，分析极端格陵兰阻塞事件的变化与气候变化和趋势的联系，并考虑极端格陵兰阻塞事件的基本物理原因(加热和/或大气环流变化)，试图了解格陵兰阻塞事件变化的原因。自然变化是阻塞的一个重要方面，格陵兰夏季阻塞最近的显著趋势是一年中全大西洋海面温度的变化--称为大西洋十年变化--与格陵兰冰盖融化和径流变化最密切的时候。因此，我们将比较模型的气候模型输出与海洋和海冰的不同表示，以确定海洋和/或北极海冰损失对格陵兰阻塞变化的可能影响。未来几十年，格陵兰夏季阻塞的持续增加将产生深远的影响：例如，加强格陵兰冰盖的融化和质量损失。最近的结果表明，冰盖表面融化和径流对气温上升的非线性加速反应，后者在一定程度上与最近夏季阻塞的增加有关。至关重要的是，理解格陵兰冰盖对未来气候变化的反应，以及由此对全球海平面上升的影响，取决于能否更好地模拟格陵兰地区的大气环流变化。因此，我们将利用我们从该项目早期工作中获得的见解和新颖的气候模型实验来评估未来格陵兰阻塞变化对北大西洋和欧洲天气和气候的可能影响，以及对格陵兰冰盖物质平衡的影响，从而评估全球海平面上升的可能影响。我们预计，我们在北大西洋这一气候关键地区的研究结果将为理解格陵兰阻塞的原因和影响向前迈出重要的一步，并有助于指导下一代全球气候模型的开发。

This project aims to provide a major advance in the understanding of the causes of atmospheric circulation changes (specifically changes in blocking or persistent high air pressure) over Greenland, their relation to variations in the North Atlantic atmospheric and oceanic circulation systems, their consequences for climate change and extreme weather conditions over Greenland and the wider North Atlantic/Northwest Europe/UK region, and their impacts on Greenland Ice Sheet mass loss and global sea-level rise.High-pressure blocking in Northern Hemisphere mid-high latitudes is an important feature of the general circulation of the atmosphere that is closely linked to the jet stream and extreme weather events over densely populated mid-latitude regions. The physical causes of blocking and consequently how it responds to and influences broader-scale climate change are poorly understood, especially in terms of connecting weather (daily) and climate (year-to-year or longer) timescales. Recent research shows a significant increase in blocking over the Greenland region, mainly in summer, since around 1990. This is not well simulated by currently available global climate models. This deficiency may be linked to recent rapid Arctic sea-ice loss which is also not well captured by the climate models. However, the latest generation of climate models show some improvement compared with earlier versions, although still have some differences between modelled and observed representations of Greenland Blocking.Our proposal addresses this model-observation mismatch by means of a comprehensive comparison using new methods, the updated observations and the latest state-of-the-art climate model simulations. We seek to understand the causes of changes in Greenland Blocking through observation-based data on a wide range of timescales from daily to decadal, analysing how changes in extreme Greenland Blocking events are linked to climatological variations and trends, and considering fundamental physical causes (heating and/or atmospheric circulation changes) of extreme Greenland Blocking events. Natural variability is an important aspect of blocking, and the recent significant trend in Greenland Blocking in summer is the time of year when changes in Atlantic-wide sea-surface temperatures - called Atlantic Multidecadal Variability - are most closely associated with melt and runoff changes from the Greenland Ice Sheet. We will therefore compare climate-model output from models with varying representations of the ocean and sea ice in order to identify possible oceanic and/or Arctic sea-ice loss influences on Greenland Blocking changes.There would be profound implications of a continued increase in Greenland Blocking in summer over the coming decades: for example, enhancing melting and mass loss of the Greenland Ice Sheet. Recent results indicate a non-linear, accelerating response of the ice sheet's surface melt and runoff to rising temperatures where the latter are partly linked with the recent blocking increase in summer. Crucially, understanding how the Greenland Ice Sheet responds to future climate change, and the resulting effects on global sea-level rise, depends upon being able to better model atmospheric circulation changes over the Greenland region. Therefore, we will use our insights gained from earlier work in the project and novel climate model experiments to evaluate the likely impacts of future Greenland Blocking changes on North Atlantic and European weather and climate, and on the Greenland Ice Sheet mass balance and hence global sea-level rise. We expect that our results from this climatically crucial part of the North Atlantic will provide a major step forward for understanding the causes and impacts of Greenland Blocking and help guide development of the next generation of global climate models.